Signaling circuit



@et 23 E923.

E. DIETZE SIGNALING CIRCUIT Filed Jan. 2e, 1921 Patented. @et 23, 1923,

hair ras e EGINHAR-D DIETZE, 0F BROOKLYN, NEVI YORK, ASSIGNOR TO AMERICAN-TELEPHONE AND TELEGR-APH COMPANY, A CORPORATION OF NEW' YORK,

SIGNALING CIRCUIT.

Application tiled January 26, 1921. Serial No. 440,087.

To all whom tmo/ concern.'

Be it known that I, EGIM-IARD Dinrzn, residing at Brooklyn, in the county of Kings and State of New York, have invented certain Improvements in Signaling Circuits, of which the following is a specification.

rlhis invention relates to circuit arrangements for signaling systems wherein signals may be either transmitted from or received at the same station. n its more specilic aspects, this invention is embodied in a subscribers telephone station hereinafter termed, in accordance with the common usage, a substation, and, more particularly, in the combination of a substation and a telephone line, the substation circuit arrangement being of the general type pro posed by George A. Campbell and described in a number of U. S. patents issued to him under date of January 22, 1.918, and numbered as follows: 1,254,116; 1,254,117 1,251,118; 1,254,471; 1,254,472; 1,254,474; 1,254,475 and 1,254,476.

As fully set forth in the patents above referred to, telephone substations of the Campbell type comprise a transmitter, receiver, auxiliary resistance and a transformer having a plurality of windings, and these elements, in combination with a tele- .'i phone line, are so designed that: (1) the transmitter and receiver are conjugate, that is, there is negligible side tone in the receiver in consequence of the actuation ot' the transmitter by sound waves; (2) the line and auxiliary resistance are conjugate, in order that none of the energy absorbed by the substation from the line. shall be wasted in said auxiliary resistance; (3) for a given Yline having a definite impedance, telephonie energy delivered by the transmitter is a maximum; (4) the amount of energy delivered by the line to the substation is a maximum-in other words, the impedance of the substation as seen 'from the line is equal to the impedance of the line; (5) at a. small sacrifice of efiiciency, it is possible to discriminate effectively against disturbing line noise, as distinguished from the telephonie signals from the communicating station.

In common battery telephone exchanges, special conditions often arisein which it is desirable to connect tothe switchboard subscribers who are further away from the oiice than can be reached with the gauges of cable usually employed for substation loops without exceeding the standard of transmission maintained forsuch exchanges.

ln such cases, in order to reduce the transter and a receiver ofthe vwell-'known electrol magnet or direct current type, the .circuit will not only have xthe advantages just stated, but it will also be an improvement from a maintenance standpoint,.,since the local battery set used on lextraordinarily long common battery lines will then employ the same transmitter and receiver which are used in the ordinary common battery sets.

It is, therefore, one of the objects of this invention to produce a substation circuit having the characteristics of the Campbelll type and which is so arranged that a local battery may be yemployed to energize 'both the transmitter and receiver, said local `battery being adapted to energize these instruments either alone or in conjunction with common battery energy supplied .from a central station, common battery energy being also employed for purposes of signaling and supervision.

Other and further objects of theinvention will be clear from the following description when read in connection with the accompanying drawing, Figure kl of which is a schematic diagram of the general type of Campbell substation circuit, from which the circuit of the present invention is .derived; Fig. 2 of which is a similar diagram of the circuit of the present invention; ,-Figs. 3 and 4 of which are diagrams showing two circuit arrangements oi. the invention in more detail; and Figs. 5 and M6 of which are diagrams illustrating the vflow ofalternating current during the ,operations off transmitting and receiving, respectively.

The general theory vof vsubstations of the type to which the Tpresent invention belongs, is fully set forth in the above mentil) `los

lli

tioned patents to George ri.. Campbell, so that it is unnecessary to present any theoretical considerations in the present instance, a simple description of the circuit arrangement being sui'iicient for a full understanding of the invention.

Referring to Figs. 2 and 3, L designates a transmission line terminating in a telephone substation arrangement comprising a transmitter T, a receiver R, an auxiliary resistance X and a transformer comprising windings N1, N2 and N2. @ne side ot the line L and one terminal of the receiver lt and the auxiliary resistance X arc joined together at a common point l. The winding ll, is joined between the other terminal of the auxiliary resistance X and the other terminal of the receiver lt, the windings N2 and N1 being connected in series between the terminals 2 and B et the line L and the receiver R, respectively. The transmitter T is connected between the common point et the windings N1 and N2 and the terminal 3 of the winding N 2, so as to be in shunt with the winding N1. ri local battery B is inserted in circuit with the winding N, tor supplying the current for the transmitter T. This battery would also supply an energizing current 'for the electromagnet receiver R through the winding N2 over the line L, through the ceiver lt and back to battery through the winding N1. The resistance ot this circuit, however, is quitehigh and, in order to provide a path ot low resistance tor the battery supply of the electromagnet receiver l, an impedance coil P is connected between the right-hand terminal or the battery B and the terminal l. The impedance coil is of low resistance, so that a large current supply is furnished to the electromagnet receiver lt over a circuit from the battery through the coil P, through the receiver and through the transmitter T, to the other terminal ot the battery. The impedance ot the coil P is made very high, however, so that, as regards the flow of alternating current in the substation circuit, the path through the impedance coil is practically an open circuit. The resistance or coil l) is so proportioned as to supply optimum direct current to the electromagnet receiver. Tt will be noted that the coil N1, which, as' ordinarily constructed in the Campbell type of substation, is of low resistance, would normally constitute a low resista-nce shunt across the circuit including the receiver R, thereby diverting current away from the receiver. ln order to prevent this a resistance l0 is included in the path of the winding N1, so that the resistance ot this path becomes suiiciently large to cause a large current to flow over the circuit previously traced, including the transmitter T and the receiver R in series. lt will be understood that in practice this resistance may be incorporated in the winding N1.

iat/nece A slight modiiication of the circuit is illustrated in Fig. This modification differs from that ot Fig. 3 in that the battery l is included between the junction point 3 of the windings N1 and N2 and the junction point ES" of the transmitter T and electromagnet receiver R. The impedance coil l?, instead ot being connected as in Fig. 3, is connected between the terminal 3 and the point l which is strapped to the terminal l of the receiver. ln accordance with this torni of the invention, the receiver R and transmitter T are in effect strapped together to the terminal Il through the battery l which, (so tar as the 'flow oi' alternating current is concerned) may be considered of negligible impedance. From this standpoint, therefore, the circuit is indenticalwith that or F ig. 3. This torni of circuit arrangement also has the advantage that it is unnecessary to provide a resistance corresponding to the resistance l0 ot Fig. 3, as there is no circuit of low impedance in shunt with the receiver R. vJliti the ba tery B connected as shown, direct current for energizing the transmitter flows through the winding N1 and the transmitter back to battery, while the direct current for energizing the receiver R Hows from the battery through the impedance coil P and 'through the receiver it back to battery.

ln so Jfar as the flow of alternating current is concerned, the two arrangements oit Figs. 3 and l are identical and differ only as regards the direct current connections. The operation of these circuits when transmitting will be as indicated in' Fig. 5, in which the arrows designate the instantaneous flow of alternating current. The diagram of Fig. 5 is simpliied by omitting the direct current apparatus and illustrating only the circuits tor the flow of alternating current and may be considered as exemplitying either the arrangement shown in Fig. 3 or Fig. le lli/Then the transmitter T is actuated, its operation is equivalent to setting up an alternating electromotive torce in the circuit ot the transmitter T, so that a current l, will iiow at a given instant in the direction indicated by the arrow to the lett of the transmitter is the transmitter T and the receiver F are conjugate, no current flows through the receiver R in response to the actuation of the transmitter T, and, therefore, the current l, which flows over the line L in response to the actuation of the transmitter T must be equal to the current l, flowing through the auxiliary resistance X. Consequently, a current equal to the difference between the transmit-` ter current l, and the line current, or its equivalent, the current T3 through the auxiliary resistance X, appears in the winding lll so that a current L-ll flows in the direction indicated by the arrow, just below the winding N1.

The operation during the receptionof siglilo nals is indicated in Fig. 6. An 'electrom'otive force applied to the line L causes the line current L., to flow through the winding of the coil N 2 in the direction indicated. As the auxiliary resistance X is conjugate with respect to the line L under these conditions, no current flows through the auxiliary resistance and, consequently, no current fiows through the winding N2. It follows, therefore, that the current I2 through the receiver must be equal to the line current I2. A. current Il will be caused to iiow. through the transmitter in t-he direction indicated by the arrow to the right of the transmitter T and a current will flow through the winding N1, in the direction indicated, this current having a value L-ll.

The circuit of the present invention isa development of the general type of circuit disclosed in Fig. 1 of Campbell Pat-ent, 1,254,472, above referred to, and the circuit type of said patent can be represented schematically as shown in Fig. 1. The operation of such a circuit as an anti-side tone circuit requires that in all cases the voltages between terminals 2 3 and 3 1 be series-aiding and of the relative magnitude jy, where 7/ is the energy distribution ratio and may be defined as the ratio of the energy in the transmitter to the energy in the receiver on receiving.

The design formulae for the general type of circuit as given in the Campbell patent are as follows:

The circuit of the present invention may be obtained from the type circuit illustrated in Fig. 1 by elimina-ting the winding N1 of Fig. 1 and bridging the transmitter across the terminal 3 and some point 5 of the winding N2, thereby giving the general type of circuit schematically illustrated in Fig. 2. This leads to an auto-transformer arrangement between the windings N1 and N2 of Fig. 1, the part of the winding N2 between the terminals 3 and 5 taking the place of the winding N2. Windings Nl and N 3 in Fig. 2 correspond respectively to the windings N1 and N 2 of Fig. 1, and the number of turns effectively in series between the terminals 2 and 3 of Fig. 2 represent the winding N2 of the circuit of Fig. 1. These turns and the turns of the winding N3 are always series-aiding as above pointed out.

There are in general a number of possible values for the winding N2 of Fig. 2, corresponding to several possible arrangements of the windings on the core. For example, all three windings in Fig. 2 may be seriesaiding, in which case the turns of winding N2 of Fig. 2 are equal to the turns of winding N2 of Fig. 1 minus the turns of winding N1 of Fig. 1. Another method of winding is to make N2 and N3 of Fig. 2 aiding, and N1 opposing, in which case the turns of winding N2 of Fig. 2 will be;equal to the turns of kwinding N1 of Fig. 1 Vplus the turns of winding N2 of Fig. 1. It is also possible to arrange the windings of Fig. 2

s0 that windings N1 a-ndyN3 of said figure will be aiding and N2 opposing. In this case the turns of winding N2 of Fig. 2 will be equal to the turns of winding N1' of Fig. 1 minus the turns of the winding N2 of Fig. l.

In practice, when lthe transmitter resistance is low, the first -of these methods of winding, that is, the one in which windings N17 N2 and N3 are series-aiding, is preferable as it requires a minimum number of turns on the transformer. The design formulae for this case may be readily obtained from the design formulae of Fig. 1 by con- Sii sidering the relations between the windings of Fig. 1 and Fig. 2, as just given. These design formulae are as follows:

ln formulae (l) and. (2) it will be understood that'R1 is the resistance of the transmitter, R2 the resistance of the receiver, R3. the .resistance of the auxiliary element and R4 the .resistance .of the line, while 'y is the energy ratio previously defined. It will be seen from these Y formulae that having given the line impedance and theresistance of the transmitter it is desired to use, the impedance of the receiver and auxiliary element and the number 4of turns of the winding of the transformer may be readily obtained by assigning any desired value to the ratio gf. As pointed out in the Campbell patent, a desirable value for y is in the neighborhood of 1.4:. It will of course be obvious that while the auxiliary element X is illustrated as a separateY resist-ance element, in practice the resistance represented by this element may be obtained by properly designing the winding N3 so that the elements N2 and X may be merged.

It will be apparent that the general principles herein disclosed may be embodied in many other organizations widely different from those illustrated without departing from the invention, as delined in the followin oclaims.

/Vha-t is claimed is:

l. ln a signaling system a transmission circuit, a transmitting circuit, a receiving circuit, a balancing circuit, and a transformer having three windings, one of said windings being included in said transmission circuit, another of said windings being included in said balancing circuit, and the third winding being included between said transmission and balancing circuits; a terminal ot each ot said transmission, receiving,

and balancing circuits being joined together, the other terminal of said receiving circuit being connected to the junction point between said third Winding and said balancing circuit; said transmitting circuit being connected in shunt with said third winding; a source of direct current so connected as to supply current to both said transmit-- ting` and receiving circuits, and a connection having large impedance and low resistance directly connected between one terminal ot said source and a terminal of said receiving` circuit.

2. ln a signaling system a transmission circuit, a transmitting circuit, a receiving circuit, a balancing circuit, and a transformer having three windings, one or' said windings being included in said transmission circuit, another of said windings being included in said balancing circuit, and the third winding being included between said transmission and balancing circuits; a terminal ot each of said transmission, receiving, and balancing circuits being joined together, the other terminal of said receiving circuit being connected to the junction point between said third winding and said balancing circuit; said transmitting` circuit being connected in shunt with said third winding; a source of direct current included in series with said third winding, and a connection having large impedance and low resistance directly connected between one terminal of said scoruce and a terminal of said receiving circuit.

3. in a signaling system a transmission circuit, a transmitting circuit, a receiving newness circuit, a balancing circuit, and a transformer having three windings, one of said windings being included in said transmission circuit, another oit said windings being included in said balancing circuit, and the third winding being included between said transmission and balancing circuits; a terminal of each of said transmission, receiving, and balancing circuits being joined together, the other terminal of said receiving circuit being connected to the junction point between said third winding and said balancing circuit; said transmitting circuit being connected in shunt with said third winding; a source or' direct current so connected as to supply current to both said transmitting and receiving circuits, and a connection of high impedance but low resistance directly connected between one terminal of said source and the terminal of said receiving cire cuit, which is joined to saidy transmission and balancing circuits.

d. In a signaling system a Aiuinsmissfion circuit, a transmitting circuit, a receiving circuit, a balancing circuit, and a transformer having three windings, one of said windings being included in said transmission circuit, another of said windings being included in said balancing circuit, and the third winding being included between said transmission and balancing circuits; a terminal of each of said transmission, receiving, and balancing circuits being joined together, the other terminal of said receiving circuit being connected to the junction point between said third winding and said balancing circuit; said transmitting circuit being connected in shunt with said third winding; a source of direct current included in series with said third winding, and a connection ot high impedance but low resistance directly connected between one terminal of said source and the terminal of said receiving circuit which is joined to said transmission and balancing circuits.

In testimony whereof, l have signed my name to this specification this 22nd day ot January 1921.

EGNHRD DET iii) 

